Seven continents: Snapshots of troubled species
August 25, 2014
EHN writer Alanna Mitchell offers a peek at species on all seven continents that depict the array of health threats that birds face. All of these are listed as critically endangered, endangered or near-threatened on the IUCN Red List.
Santa Marta parakeet, Pyrrhura viridicata
This tiny bright green bird with flashes of red feathers lives only in a small patch of humid forest high in the majestic Sierra Nevada mountains in Colombia. The parakeet is famous to birdwatchers all over the world for the way it flies in small, screeching flocks that twist like a single organism among the highest reaches of the trees.
Everybody thought these parakeets were doing well until a couple of decades ago, when scientists realized that the government had doused tens of thousands of acres of marijuana and coca plantations with the herbicide glyphosate, destroying great swaths of its habitat. Its main ongoing threat is habitat loss.
Farmers and loggers razed much of the remaining humid mountain forest to plant non-native cash crops of pine and eucalyptus trees and to raise cattle. Today, 85 percent of the original forest is gone and the parakeets are in decline, and the parakeet is classified as endangered. Between 3,300 and 6,700 of the birds remain; scientists do not have a reliable estimate of their original population.
Réunion harrier, Circus maillardi
Long considered ill omens by humans, the males of this ferocious inky predator with its striking white belly are fond of putting on spectacular forest displays, calling loudly as they soar. When it comes to warning potential foes away from breeding sites and forest-floor nests, their song changes to a harsh, grating cry.
Only about 130 breeding pairs remain on the planet, with an estimated 560 adults in all. They live exclusively on the French-owned island of Réunion in the Indian Ocean off the coast of Madagascar, pushed into living quarters that are far from ideal as islanders cut down the forest for crops and towns.
Where once the harriers feasted entirely on insects and other birds, today about half of their diet comes from rats, mice and other small, nonnative mammals introduced onto the island. But along with the animals, they consume the lethal poison that islanders use to kill rodents. Those inadvertent deaths, along with deliberate kills as people poach them and exterminate them for preying on poultry, are the biggest threats to Réunion harriers today. Other threats include crop pesticides, cyclones and heavy rains.
Indian vulture, Gyps indicus
White-rumped vulture, Gyps bengalensis
Slender-billed vulture Gyps tenuirostris
Status: Critically endangered
Adelie penguin Pygoscelis adeliae
Adelie penguins, with their snow-white bellies, black heads and backs, stubby wings and amusing waddles, live on the only continent that’s supposed to be protected from humanity’s impact. There’s no cities, mining, industry, logging or agriculture. The continent, covered with more than a mile’s thickness of ice and set aside by global treaty for science and nature, seems devoid of human impact.
But it’s not quite that simple. Research stations have released flame retardants and other pollutants into the pristine environment, contaminating Adelie penguins. The biggest threat, however, is that their numbers have fluctuated along with the numbers of whales, which feast on krill, the penguins’ favorite food. When whales were hunted up until the end of World War II, penguin populations soared. When the world ended commercial whaling in 1986, they dropped. Today, their numbers are on the wane and their chicks weigh less, according to longtime penguin researcher Wayne Trivelpiece of the National Oceanic and Atmospheric Administration. That’s partly because there is less krill. But it’s also because of changes to the ocean itself stemming from climate change, Trivelpiece said.
Adelie penguin numbers are still strong: Nearly 5 million adults. The concern is that climate change is advancing more rapidly in the western peninsula of Antarctica than anywhere else. That could eventually kill all Adelies north of about 68 degrees south latitude by melting the sea ice that supports krill.
Ashy Storm-Petrel, Oceanodroma homochroa
This small seabird hatches its eggs in rocky crevices on 17 islands off California and Baja Mexico, returning to the same mate and same nest year after year. Today, only about 10,000 Ashy storm-petrels remain, a population sharply lower than during the first half of the 20th century. From 1972 to 1992 alone, the number of breeding birds fell by 42 percent. The declines persisted through the 1990s, with an absence of nests on several islands once commonly inhabited by these dusky grey birds. On the South Farallon Islands off San Francisco, a study showed the number of petrels dropped by 78 percent over half a century.
The main cause of their decline has been the pesticide DDT, which contaminated the fish and squid they ate and thinned their eggshells. DDT was banned in the United States in 1972 but was still thinning their shells and killing embryos as recently as 1997, according to a recent study.
By 2008, DDT was no longer a significant factor in the petrels’ reproduction. Most breed in protected areas: Channel Islands National Park and Farallon National Wildlife Refuge. Although they were denied Endangered Species Act protection last year, they remain under threat from predators – gulls, owls, rats and cats – as well as warming waters, sea-level rise and ocean acidification.
Red kite, Milvus milvus
This graceful raptor with its red underbelly, silvery head and elegant black-tipped wings has been both loved and hated in the European countryside for centuries because it eats carrion. In medieval England, lawmakers put a bounty on its head, calling it a “vermin tax,” fearing it was taking food from the mouths of the poor.
Red kites are faithful mates that stay together for life, tending to build messy nests in tree branches. About 95 percent of its breeding grounds is in Europe, with a small population edging into Asia. Most of the global population – now between 21,000 and 25,500 breeding pairs – once wintered in Spain. But many of the birds now stay put for the winter.
The kites’ global numbers dropped alarmingly until the 1970s because of poison. Landowners in the United Kingdom, France and Spain set out poisons to kill foxes, wolves, crows and voles preying on livestock, game and crops. Red kites took the bait instead and died.The Spanish government applied more than 1,500 tons of rodenticides on a wide swath of farmland in 2007 and 2008, so red kites were hard hit during those years.
Their numbers declined 16 percent over the past 35 years, and they are still decreasing in Spain, France and Germany. But they are rebounding in the United Kingdom and in Sweden, Poland and Switzerland. Today, while still a bird of concern because the losses continue to offset the gains, the red kite is considered a global success story. Nicola Crockford of BirdLife International said campaigns to help United Kingdom gamekeepers realize that the poisons were killing off the birds have worked well. That, plus the reintroduction of kites to the United Kingdom, mean that this year for the first time in a decade, she saw a red kite near her home in East Anglia.
|Christmas Island Seabird Project|
Abbott’s booby, Papasula abbotti
Christmas Island frigatebird, Fregata andrewsi
Christmas Island, a chunk of coral jutting out of the Indian Ocean far off the coast of Australia, is a globally-important resting and breeding site for birds. In the late 19th century, phosphate was discovered, launching a mining industry which cut down wide swaths of the rainforest. A century later, the two species of seabirds that can breed only on this island are in trouble: the Abbott’s booby and the Christmas Island frigatebird.
|Christmas Island Seabird Project|
The population of the black and white Abbott’s booby, the world's rarest booby, has shrunk to only 6,000 adults, a drop of one-third to one-half over the past century. Part of the problem is that the booby is a relatively unenthusiastic breeder: It builds precarious nests in tall rainforest trees and will lay only one egg a year, then takes a break for a full year. By the early 1990s, one-third of its historic nesting space had fallen to clearcutting for the mines. In 2007, another round of clearing began. More clearing and a satellite launch pad have been proposed. The boobies may also be harmed by the yellow crazy ant, an introduced species that began to form super-colonies in the 1990s. Extreme weather events spawned by climate change also are threats.
The huge Christmas Island frigatebird, with its broad wingspan, forked tail, swooping flight paths and, in breeding season, startlingly red, inflated chest pouches in the male, is an increasingly rare sight. Already the rarest frigatebird in the world, its adult population rests between 2,400 and 4,800 and is declining, along with the ever-smaller piece of Christmas Island suitable for its breeding. Their numbers plummeted by an estimated 66 percent over the past half-century, partly the result of clearcutting and mining dust. A picky bird, it can take more than a decade to pair up again if it loses its mate, and it produces only a single chick every two years. But it is also determined: It will fly non-stop for weeks on end to get food for its chick – one female was tracked flying 4,000 kilometers over 26 days – snatching fish from the sea or stealing another animal’s hard-won catch. Two-thirds of their tall-tree nests are in a single spot, which makes the whole population vulnerable to cyclones.
On the positive side, much of the island has been turned into a national park and the mining company, Christmas Island Phosphates Pty Ltd., has agreed to stop clearing old-growth rainforest.
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